Lignocelluosic biomass is an attractive feedstock for the production of biofuels, chemicals, and bioproducts. Lignocellulosic biomass provides many benefits, including abundant availability, potential low cost, sustainability, and the fact that it is not ordinarily consumed by humans as a source of food (Langeveld J W A et al. 2010 Crop Sci 50: S131-S151). To convert lignocellulosic biomass into renewable energy and biochemicals, bioprocesses convert a portion of the lignocellulosic biomass into simple sugars, which are converted into biofuels or other bioproducts.
The cost of sugar production through biological conversion is expensive due to the costs of biomass pretreatment and enzymatic hydrolysis (Alvira P et al. 2010 Bioresour Technol 101: 4851; Abramson M et at 2010 Plant Science 178: 61; Daniel Klein-Marcuschamer et al. Biotechnol. Bioeng. 2012; 109:1083). Plant cell walls are recalcitrant to enzymatic hydrolysis because the heterogeneity, chemical composition and structural features of the cell wall polysaccharides make them inaccessible to hydrolytic enzymes (Zhu L et al. 2008 Bioresour Technol 99: 3817). For this reason, enzymatic hydrolysis requires a pretreatment that can make plant cell walls accessible. The pretreatment technologies prevalent in industry typically employ harsh conditions such as high temperatures and extreme pHs (Wyman C E et al. 2005 Bioresour Technol 96:1959; Mosier N et at 2005 Bioresour Technol 96: 673). These conditions cause sugar degradation and result in reduced sugar yields and formation of toxic fermentation compounds, requiring expensive additional steps for detoxification, separation and neutralization as well as expensive up-front capital equipment.
Pretreatment costs, high costs of exogenous enzyme loadings, slow hydrolysis rate, and limited supply of enzymes are also concerns for the commercialization of processes involving lignocellulosic biomass.